Loop heat pipe with flexible artery mesh

ABSTRACT

A loop heat pipe ( 10 ) includes an evaporator ( 11 ) thermally connected with a heat generating electronic component and including a wick structure ( 112 ) disposed therein, a condenser ( 12 ) thermally connected with a heat dissipating component, a vapor line ( 13 ) and a liquid line ( 14 ) connecting the evaporator with the condenser to form a closed loop, a predetermined quantity of bi-phase working medium contained in the closed loop, and an artery mesh ( 15 ) located within the liquid line.

1. FIELD OF THE INVENTION

The present invention relates generally to a loop heat pipe for transferor dissipation of heat from heat-generating components, and moreparticularly to a loop heat pipe with flexible artery mesh disposedtherein for improving heat dissipation for the heat-generatingcomponents.

2. DESCRIPTION OF RELATED ART

Loop heat pipes have excellent heat transfer performance due to theirlow thermal resistance, and are therefore an effective means fortransfer or dissipation of heat from heat-generating components such ascentral processing units (CPUs) of computers.

A conventionally loop heat pipe includes an evaporator thermallyconnected with a CPU and disposing a wick structure therein, a condenserthermally connected with a heat sink, a vapor line and a liquid linedisposed between and connecting the evaporator with the condenser, acompensation disposed between the wick structure and the liquid line,and a predetermined quantity of bi-phase working medium contained in theevaporator and the liquid line.

During operation of the loop heat pipe, the working medium in theevaporator absorbs heat from the CPU and vaporizes, thus generating avapor pressure which propels vaporized working medium towards thecondenser via the vapor line. The vaporized working medium dissipatesthe heat to the heat sink at the condenser and condenses to liquidthereat. The condensed working medium is then propelled through theliquid line, the compensation and the evaporator in that order by thevapor pressure and by capillary action generated by the wick structure.The condensed working medium at the evaporator then evaporates and iscondensed to liquid thus perpetuating the cycle.

In the operation of the loop heat pipe, the working medium at theevaporator needs to be heated to vaporize and generate enough vaporpressure to conquer gravitational force acting on the working medium inthe liquid line so as to power the circulation of the working fluid.Therefore, a start up temperature must first be achieved before the heatpipe can operate, which troubles the loop heat pipe to be operated in alower temperature.

Therefore, it is desirable to provide a loop heat pipe which has bettergravity conquest capability and easily to be operated under lowertemperature.

SUMMARY OF THE INVENTION

The present invention relates to a loop heat pipe for removing heat fromheat-generating components. The loop heat pipe includes an evaporatorwith a wick structure disposed therein and thermally connected with aheat generating electronic component, a condenser thermally connectedwith a heat dissipating component, a vapor line and a liquid lineconnecting the evaporator with the condenser to form a closed loop, witha predetermined quantity of bi-phase working medium contained in theclosed loop, and an artery mesh disposed within the liquid line.

Other advantages and novel features of the present invention will becomemore apparent from the following detailed description of preferredembodiment when taken in conjunction with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present invention can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present invention. Moreover,in the drawings, like reference numerals designate corresponding partsthroughout the several views:

FIG. 1 is a loop heat pipe in accordance with a preferred embodiment ofthe present invention;

FIG. 2 is an enlarged transverse cross-sectional view of the loop heatpipe of FIG. 1, taken along line II-II;

FIG. 3 is an enlarged transverse cross-sectional view of the loop heatpipe of FIG. 1, taken along line III-III;

FIG. 4 is an enlarged view of a circled portion IV of the loop heat pipeof FIG. 1;

FIG. 5 is an enlarged transverse cross-sectional view of the loop heatpipe of FIG. 1, taken along line V-V;

FIG. 6 is a front view of an artery mesh of the loop heat pipe of FIG.1; and

FIG. 7 a transverse cross-sectional view of the artery mesh of the FIG.6, taken along line VII-VII.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a loop heat pipe 10 in accordance with a firstembodiment of the present invention. The loop heat pipe 10 includes anevaporator 11 thermally connected with a heat generating electroniccomponent such as a CPU (not shown), a condenser 12 thermally connectedwith a heat dissipating component such as a heat sink (not shown), vaporand liquid lines 13, 14 connecting the evaporator 11 with the condenser12 to form a closed loop, a predetermined quantity of bi-phase workingmedium (not labeled) contained in the closed loop, and a flexibleinterwoven artery mesh 15 disposed within the liquid line 14.

Referring particularly to FIGS. 2 and 3, the evaporator 11 is a hollowtube which contains a wick structure 112 coextensive with a centrallongitudinal axis of the evaporator 11. The wick structure 112 istubular shaped in profile and has a column shaped outer wall 113contacting with an inner wall of the evaporator 11. The wick structure112 has a closed end 114 abutting against the liquid line 14 and an openend 115 abutting against the vapor line 13. A column-shaped vaporchannel 116 communicating with an inner space of the vapor line 13 isdefined in a middle portion along a central longitudinal axis of thewick structure 112. A diameter of the vapor channel 116 is larger than adiameter of an inner wall of the vapor line 13, thus increasing the flowrate of vaporized working medium entering into the inner space of thevapor line 13. The wick structure 112 in the evaporator 11 of the loopheat pipe 10 can, for example, consist of porous structures, such asfine grooves integrally formed at the inner wall of the evaporator 11,screen mesh or fiber inserted into the evaporator 11 and held againstthe inner wall thereof, or sintered powders combined to the inner wallof the evaporator 11 using a sintering process.

The condenser 12 is disposed distant from the evaporator 11 and has alower temperature than that of the evaporator 11, thus causing thevaporized working medium to be condensed. The condenser 12 is a heatsink including a plurality of fins (not shown) for increasing heatdissipation area thereof so as to benefit the condensation of thevaporized working medium. An end of the liquid line 14 extends into thecondenser 12 and connects with the vapor line 13 so that the vaporizedworking medium is condensed at the condenser 12 and is directlypropelled towards the evaporator 11. Alternatively, the condenser 12 maybe a cooling chamber, with the liquid line 14 and the vapor line 13separating from each other and respectively connecting with two ends ofthe chamber. Under this status, the vaporized working medium enters intothe condenser 12 and is condensed thereat. The condenser working mediumin the condenser 12 enters into the liquid line 14 and is propelledtowards the evaporator 11.

The vapor and the liquid lines 13, 14 are made of deformable materialscompatible with the working medium, such as aluminum, stainless steel,or plastics. Each of the vapor and liquid lines 13, 14 includes twoparallel sections 13 a and 13 b/14 a and 14 b with two correspondingends thereof connecting with the respective ends of the evaporator 11and the condenser 12, and a perpendicular section 13 c/14 c with twoends thereof connecting with the other two ends of the parallel sections13 a and 13 b/14 a and 14 b.

The working medium is usually selected from a liquid which has a lowboiling point such as water, methanol, or alcohol. Thus, the workingmedium can easily evaporate to vapor when it receives heat in theevaporator 11 and condense to liquid when it dissipates heat in thecondenser 12.

Referring to FIGS. 4 to 7, the artery mesh 15 is an elongated hollowtube, which is attached to and extends along an inner wall of the liquidline 14. The artery mesh 15 is woven from a plurality of metal wires 151(FIG. 6), such as copper, or stainless steel wires. Alternatively, theartery mesh 15 can be formed by weaving a plurality of non-metal threadssuch as fiber together. A first channel 152 is defined in an inner spaceof the artery mesh 15, whilst a second channel 153 is defined between anouter wall of the artery mesh 15 and the inner wall of the liquid line14 for passage of the condensed working medium. A plurality of pores(not shown) are formed in a peripheral wall of the artery mesh 15, whichprovide capillary action to the working medium and communicate the firstchannel 152 with the second channel 153. The artery mesh 15 has aring-like transverse cross section, a diameter of which is smaller thana diameter of the liquid line 14. The artery mesh 15 has a linearcontact with the inner wall of the liquid line 14 thereby defining anadjacent portion 154 contacting with the inner wall of the liquid line14 and a distal portion 155 spaced a distance from the inner wall of theliquid line 14 along a radial direction of the loop heat pipe 10. In thepresent loop heat pipe 10, the artery mesh 15 may be loosely insertedinto the liquid line 14 with some portions thereof isolated from theinner walls thereof.

In operation of the loop heat pipe 10, the working medium in theevaporator 11 absorbs heat from the heat generating electronic componentand evaporates. A vapor pressure is generated due to the vaporization ofthe working medium and propels the vaporized working medium into thevapor line 13 and towards the condenser 12. The vaporized working mediumlooses its heat to the heat dissipating component at the condenser 12and condenses to liquid to accumulate in the condenser 12 and the arterymesh 15 thereat. The condensed working medium in the condenser 12 ispropelled towards the liquid line 14 and into the evaporator 11 via thevapor pressure and the capillary force generated by the artery mesh 15and the wick structure 112. The condensed working medium then evaporatesto vapor thus perpetuating a cycle in the loop heat pipe andcontinuously absorbing heat from the heat generating electroniccomponent and dissipate the heat to the heat dissipating component.

In the present loop heat pipe 10, the capillary force generated by theartery mesh 15 conquers the gravity action of the condensed workingmedium and helps to propel the condensed working medium to enter intothe evaporator 11 via the liquid line 14. Therefore, the vapor pressureexerted on the condensed working medium is decreased, and the start uptemperature needed to generate the vapor pressure is accordinglydecreased. This results in the dependence of the start up temperature ofthe loop heat pipe 10 not being limited by the gravity action of thecondensed working medium. Thus, the loop heat pipe 10 is easy to beoperated under a lower temperature and is preferably used fordissipating heat generated by heat sensitive electronic components.

As compared to a conventional loop heat pipe with a plurality of vaporchannels defined between an inner wall of the evaporator and an outerwall of the wick structure, the wick structure 112 of the present loopheat pipe 10 has a larger contacting area for the inner wall of theevaporator 11. The larger contacting area of the inner wall of theevaporator enables the heat generating electronic component to transfermore heat to the working medium in the evaporator 11 and thereforeincreases the heat dissipation efficiency of the present loop heat pipe10. Moreover, the wick structure 112 has a simpler structure than theconventional loop heat pipe, which simplifies the manufacture thereof.Furthermore, a part of the condensed working medium is accommodated inthe artery mesh of the present loop heat pipe 10, which compensates forthe working medium in the evaporator 11 which evaporates to vapor, thuspreventing the drying out of the evaporator. Thus, there is no need tofor additional compensation in the evaporator 11 thus preventing theworking medium therein from drying out, which reduces the volume of theevaporator 11 of the present loop heat pipe 10.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size, and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

1. A loop heat pipe comprising: an evaporator configured for thermallyconnecting with a heat generating electronic component and comprising awick structure disposed therein; a condenser configured for thermallyconnecting with a heat dissipating component; a vapor line and a liquidline connecting the evaporator with the condenser to form a closed loop;a predetermined quantity of bi-phase working medium filled in the closedloop; and an artery mesh positioned within the liquid line.
 2. The loopheat pipe of claim 1, wherein the artery mesh has a linear contact withan inner wall of the liquid line.
 3. The loop heat pipe of claim 1,wherein a diameter of a cross section of the artery mesh is smaller thanthat of the liquid line.
 4. The loop heat pipe of claim 1, wherein theartery mesh is a flexible hollow tube woven from a plurality of metalwires.
 5. The loop heat pipe of claim 4, wherein the material of themetal wires is selected from a group consisting of copper wires andstainless steel wires.
 6. The loop heat pipe of claim 1, wherein theartery mesh is formed by weaving a plurality of fiber together.
 7. Theloop heat pipe of claim 1, wherein the wick structure is selected fromthe group consisting of grooves, sintered powder, fiber and screen mesh.8. The loop heat pipe of claim 1, wherein the wick structure is tubularshaped in profile and disposed in an inner wall of the evaporator. 9.The loop heat pipe of claim 1, wherein the wick structure has a closedend contacting with the liquid line and an open end communicating withthe vapor line, a vapor channel being defined in a middle portion of theopen end.
 10. A loop heat pipe comprising: an evaporator configured forthermally connecting with a heat generating electronic component andcomprising a wick structure disposed therein; a condenser configured forthermally connecting with a heat dissipating component; a vapor lineconnecting an open end of the wick structure with the condenser; aliquid line connecting a closed end of the wick structure with thecondenser; a vapor channel defined in a middle portion of the open endof the wick structure and communicating with the vapor line; an arterymesh positioned within the liquid line; and a predetermined quantity ofbi-phase working medium contained in the loop heat pipe.
 11. The loopheat pipe of claim 10, wherein the artery mesh is a hollow tube incontact with an inner wall of the liquid line.
 12. The loop heat pipe ofclaim 10, wherein a diameter of a cross section of the artery mesh issmaller than that of the liquid line.
 13. The loop heat pipe of claim10, wherein the artery mesh is woven from a plurality of metal wiresselected from a group consisting of copper and stainless steel wires.14. The loop heat pipe of claim 10, wherein the artery mesh is tightlyattached to inner walls of the liquid line.
 15. The loop heat pipe ofclaim 10, wherein the wick structure has a column shaped outer wallcontacting with an inner wall of the evaporator.
 16. The loop heat pipeof claim 10, wherein a diameter of the vapor channel is larger than adiameter of an inner wall of the vapor line.